Phillip J. Eby a écrit : > At 03:12 PM 9/28/2005 +0200, Reinhold Birkenfeld wrote: [...] > Yes. See: > > http://www.python.org/2.0/new-python.html#SECTION000700000000000000000 > > The purpose of the augmented assignment forms is to allow for the > possibility that the item's __i*__ method may or may not exist, and may or > may not return the same object. In the case where there is no __i*__ form, > or it does not return the same object, the lvalue *must* be re-bound to the > new value, or the semantics break. > > > >>A case where this matters is here: http://python.org/sf/1306777 > > > I've closed it as invalid; the behavior is as-defined.
Rather than closing this as invalid, it would be wiser to update the documentation before ! Nothing corresponds to the current behavior. I think that in this page : http://docs.python.org/ref/augassign.html The last paragraph whould be replace by : """ For targets which are attribute (or indexed) references, the initial value is retrieved with a getattr() (resp. __getitem__) and the result is assigned with a setattr() (resp. __setitem__). Notice that the two methods do not necessarily refer to the same variable. When getattr() refers to a class variable, setattr() still writes to an instance variable. For example: """ That way it will be clearly defined in the documentation. Now, one can wonder if the augmented assignment is really an improvement. Lots of errors are made because they are counter-intuitive. For example, in the standard library, I found very few uses of "+=" with a mutable object, and none would be broken if "a += b" is to be replaced by "a = a+b". At worst, there will be a performance issue that will easily be fixed by using "extend" method for lists and corresponding methods for other objects. My opinion is, redefining the augmented assignment is a problem given the assignment semantic, and perhaps we should get rid of it. Pierre -- Pierre Barbier de Reuille INRA - UMR Cirad/Inra/Cnrs/Univ.MontpellierII AMAP Botanique et Bio-informatique de l'Architecture des Plantes TA40/PSII, Boulevard de la Lironde 34398 MONTPELLIER CEDEX 5, France tel : (33) 4 67 61 65 77 fax : (33) 4 67 61 56 68 _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
